3D detection technology of fracture effectivity on acoustic logging
Fracture is one of the core parameters of reservoir evaluation for carbonate,tight sand and shale reservoirs.Acoustic logging series is not affected by mud conductivity,and the collection is convenient and economical.Based on the quantitative parameters of ultrasonic imaging fractures and the S-wave and Stoneley wave logging information of array acoustic wave,a set of fracture effectiveness classification and evaluation scheme is established in this paper.Ultrasonic imaging logging has high accuracy in identifying fractures.Induced fractures and natural fractures can be distinguished by the difference in their occurrence.In combination with energy attenuation and dispersion characteristics,cross dipole array acoustic logging can realize qualitative detection of fracture development section.According to the distribution of fracture in space,combined with the longitudinal resolution of different acoustic logging instruments and the lateral detection depth,the effectiveness of fracture can be divided into two categories:longitudinal opening and transverse validity.The larger the fracture width and Stoneley wave permeability calculated by ultrasonic imaging,the better the longitudinal fracture opening.The longer the ultrasonic imaging fracture length is,the greater the shear wave energy attenuation is,and the greater the change of the S-wave spectrum of the near and far probes in the array acoustic wave are,the better the transverse elongation of the fracture is.The strata with both longitudinal fracture opening and transverse fracture extension are evaluated as fracture developed strata.If the fractures are only longitudinally open,it is evaluated as a generally developed stratum.According to the basic principle of factor analysis in multivariate analysis,the correlation coefficient matrix of fracture characteristic parameters was constructed,and the weight coefficient of main factor variables was selected to establish the validity discrimination factor of fracture space and achieve quantitative evaluation of fracture development intervals.The above methods have been applied to granite reservoirs in Qiongdongnan Basin in the western South China Sea,highlighting the advantages of acoustic logging series in fine fracture evaluation and providing technical support for oil companies to formulate more economical and effective production plans.
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